Magnetic recording medium, production process thereof, and magnetic recording and reproducing apparatus

Abstract

A magnetic recording medium exhibiting excellent recording and reproduction characteristics is disclosed. A magnetic recording medium includes a non-magnetic substrate 1 ; a soft magnetic undercoat film 2 ; an orientation-regulating film 3 ; a perpendicular magnetic film 4 ; and a protective film 5 , the films being formed on the substrate 1 . The soft magnetic undercoat film 2 contains a material represented by the following composition: aFe-bCo-cM-dX1-fN where M is one or more elements selected from Ti, Zr, Nb, Hf, Ta, V, and Mo; X1 is one or more elements selected from Cr, Ga, Al, Si, and Ni; and a, b, c, d, and f represent atomic percentages and satisfy the following relations: 60≦a+b≦90, 30≦a≦90, 5≦c≦20, 0.1≦d≦7, and 3≦f≦30.

What is claimed is:  
     
       1. A magnetic recording medium comprising a non-magnetic substrate; a soft magnetic undercoat film containing at least a soft magnetic material; an orientation-regulating film for regulating the crystal orientation of a film provided directly thereon; a perpendicular magnetic film in which easy-magnetization axes are mostly oriented vertically with respect to the substrate; and a protective film, the films being formed on the substrate, wherein the soft magnetic undercoat film contains a material represented by the following composition: 
       
         
           aFe-bCo-cM-dX1-fN  
         
       
       wherein M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo; X1 is one or more elements selected from the group consisting of Cr, Ga, Al, Si, and Ni; and a, b, c, d, and f represent atomic percentages and satisfy the following relations: 60≦a+b≦90, 30≦a≦90, 5≦c≦20, 0.1≦d≦7,and 3≦f≦30.  
     
     
       2. A magnetic recording medium comprising a non-magnetic substrate; a soft magnetic undercoat film containing at least a soft magnetic material; an orientation-regulating film for regulating the crystal orientation of a film provided directly thereon; a perpendicular magnetic film in which easy-magnetization axes are mostly oriented vertically with respect to the substrate; and a protective film, the films being formed on the substrate, wherein the soft magnetic undercoat film contains a material represented by the following composition: 
       
         
           aFe-bCo-cM-eX2-fN  
         
       
       wherein M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo; X2 is one or more elements selected from the group consisting of P, C, B, and O; and a, b, c, e, and f represent atomic percentages and satisfy the following relations: 60≦a+b≦90, 30≦a≦90, 5≦c≦20, 0.1≦e≦10, and 3≦f≦30.  
     
     
       3. A magnetic recording medium comprising a non-magnetic substrate; a soft magnetic undercoat film containing at least a soft magnetic material; an orientation-regulating film for regulating the crystal orientation of a film provided directly thereon; a perpendicular magnetic film in which easy-magnetization axes are mostly oriented vertically with respect to the substrate; and a protective film, the films being formed on the substrate, wherein the soft magnetic undercoat film contains a material represented by the following composition: 
       
         
           aFe-bCo-cM-dX1-eX2-fN  
         
       
       wherein M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo; X1 is one or more elements selected from the group consisting of Cr, Ga, Al, Si, and Ni; X2 is one or more elements selected from the group consisting of P, C, B, and O; and a, b, c, d, e, and f represent atomic percentages and satisfy the following relations: 60≦a+b ≦90, 30≦a≦90, 5≦c≦20, 0.1≦d≦7, 0.1≦e≦7, and 3≦f≦30.  
     
     
       4. The magnetic recording medium according to  claim 3 , wherein a through f satisfy the following relations: 60≦a+b≦80, 30≦a≦80, 5≦c≦20, 0.1≦d≦3, 0.1≦e≦5, and 8≦f≦25. 
     
     
       5. The magnetic recording medium according to any one of  claims 1  to  3 , wherein the soft magnetic undercoat film comprises fine crystals containing Fe as a primary component and having an average grain size of 13 nm or less, and an amorphous phase containing M (M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo) and N in amounts greater than those contained in the fine crystals. 
     
     
       6. The magnetic recording medium according to  claim 5 , wherein the fine crystals have a bcc structure. 
     
     
       7. The magnetic recording medium according to any one of  claims 1  to  3 , wherein the soft magnetic undercoat film has a saturated magnetic flux density (Bs) of at least 1 T. 
     
     
       8. The magnetic recording medium according to any one of  claims 1  to  3 , wherein the soft magnetic undercoat film has a saturated magnetic flux density (Bs) of at least 1.4 T. 
     
     
       9. A magnetic recording medium according to any one of  claims 1  to  3 , wherein the product of the saturated magnetic flux density (Bs) and thickness (t) of the soft magnetic undercoat film is at least 50 T·nm. 
     
     
       10. The magnetic recording medium according to any one of  claims 1  to  3 , wherein the product of the saturated magnetic flux density (Bs) and thickness (t) of the soft magnetic undercoat film is at least 100 T·nm. 
     
     
       11. The magnetic recording medium according to any one of  claims 1  to  3 , wherein the orientation-regulating film comprises an hcp-structure material containing one or more elements selected from the group consisting of Ti, Zn, Y, Zr, Ru, Re, Gd, Tb, and Hf in a total amount of at least 50 at %. 
     
     
       12. The magnetic recording medium according to any one of  claims 1  to  3 , wherein the orientation-regulating film comprises an fcc-structure material containing one or more elements selected from the group consisting of Ni, Cu, Pd, Ag, Pt, Ir, Au, and Al in a total amount of at least 50 at %. 
     
     
       13. The magnetic recording medium according to any one of  claims 1  to  3 , wherein a portion or the entirety of a surface of the soft magnetic undercoat film facing the perpendicular magnetic film is oxidized. 
     
     
       14. The magnetic recording medium according to any one of  claims 1  to  3 , wherein the perpendicular magnetic film has a nucleation field (−Hn) of at least 0 (Oe). 
     
     
       15. A process for producing a magnetic recording medium, which comprises forming, in order, on a non-magnetic substrate, a soft magnetic undercoat film containing at least a soft magnetic material, an orientation-regulating film for regulating the crystal orientation of a film provided directly thereon, a perpendicular magnetic film in which easy-magnetization axes are mostly oriented vertically with respect to the substrate, and a protective film, wherein the soft magnetic undercoat film contains a material represented by the following composition: 
       
         
           aFe-bCo-cM-dX1-eX2-fN  
         
       
       wherein M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo; X1 is one or more elements selected from the group consisting of Cr, Ga, Al, Si, and Ni; X2 is one or more elements selected from the group consisting of P, C, B, and O; and a, b, c, d, e, and f represent atomic percentages and satisfy the following relations: 60≦a+b ≦90, 30≦a≦90, 5≦c≦20, 0.1≦d≦7, 0.1≦e≦7, and 3≦f≦30.  
     
     
       16. A process for producing a magnetic recording medium according to  claim 15 , wherein the soft magnetic undercoat film comprises fine crystals containing Fe as a primary component and having an average grain size of 13 nm or less, and an amorphous phase containing M (M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo) and N in amounts greater than those contained in the fine crystals. 
     
     
       17. A process for producing a magnetic recording medium according to  claim 15  or  16 , wherein the soft magnetic undercoat film is formed through sputtering, and a gas employed for film formation contains nitrogen in an amount of 0.1 to 50 vol %. 
     
     
       18. A process for producing a magnetic recording medium according to any one of claims  15  or  16 , wherein, after the soft magnetic undercoat film is formed, subjecting the soft magnetic undercoat film to heat treatment at 250° C. to 450° C. 
     
     
       19. A magnetic recording and reproducing apparatus comprising a magnetic recording medium and a magnetic head for recording data onto the medium and reproducing the data therefrom, wherein the magnetic head is a single-pole head, and the magnetic recording medium comprises a non-magnetic substrate, a soft magnetic undercoat film containing at least a soft magnetic material, an orientation-regulating film for regulating the crystal orientation of a film provided directly thereon, a perpendicular magnetic film in which easy-magnetization axes are mostly oriented vertically with respect to the substrate, and a protective film, the films being formed on the substrate, wherein the soft magnetic undercoat film contains a material represented by the following composition: 
       
         
           aFe-bCo-cM-dX1-eX2-fN  
         
       
       wherein M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo; X1 is one or more elements selected from the group consisting of Cr, Ga, Al, Si, and Ni; X2 is one or more elements selected from the group consisting of P, C, B, and O; and a, b, c, d, e, and f represent atomic percentages and satisfy the following relations: 60≦a+b ≦90, 30≦a≦90, 5≦c≦20, 0.1≦d≦7, 0.1≦e≦7, and 3≦f≦30.  
     
     
       20. A magnetic recording and reproducing apparatus according to  claim 19 , wherein the soft magnetic undercoat film comprises fine crystals containing Fe as a primary component and having an average grain size of 13 nm or less, and an amorphous phase containing M, wherein M is one or more elements selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, and Mo and N in amounts greater than those contained in the fine crystals. 
     
     
       21. A process for producing a magnetic recording medium according to  claim 17 , wherein, after the soft magnetic undercoat film is formed, subjecting the soft magnetic undercoat film to heat treatment at 250° C. to 450° C.